To understand how salt affects blood pressure, we need to do a bit of time travel – travelling back in time to the period when humans used to wander vast distances on foot in search of areas with ample game, water and shelter. But before we do that, let us understand why humans need salt.

Understanding why we need salt

Our body uses salt as a catalyst to improve conductivity. It is the electrical conductor flowing in the blood and is used to transmit information to and from our brain to the rest of the body. Salt is also required to absorb nutrients from our small intestines. The human body does not make salt so it extracts it from foods that might contain salt.

Let us now go back in time to the period when our ancestors used to wander vast distances and often away from water and food sources. Since salt was an important nutrient for the body, our kidneys evolved to concentrate urine and retain salt so that the information flow from the brain to the rest of the body was always maintained at an optimal level even during times of scarce water and food. Salt also helped retain water in the body thus helping keep away dehydration for as long as possible – like everything else that developed during those early days, it was a basic survival strategy.

This went on for almost a million years. Over the last couple of hundred years or so, humans evolved a bit too fast and genetic evolution was left far behind. Today other than fruit, just about everything else we eat contains salt. We add large quantities of it in everything that is cooked.

Salt overload

When we consume too much salt, our kidneys attempt to maintain the balance by eliminating the excess through urine and sweat. Unfortunately, our kidneys are more efficient at retaining salt then eliminating it (after all, for almost a million years it was perfecting the art of retaining water and salt).

Add to this our lack of exercise and also working in air conditioned environment i.e. we do not sweat as much as our forefathers did. This meant that our kidneys had only one way to eliminate excess salt – through urine.

Effects of Salt Overload

Excessive salt leads to higher water retention which in turn leads to excessive fluid pressure on blood vessel walls. When this happens, the blood vessels activate a defence mechanism of their own – the walls of the blood vessels thicken (to prevent rupture) and also get narrow to create bottlenecks so pressure is reduced.

How salt affects blood pressure

When the defence mechanism of the blood vessels kicks in, the organs in the body start crying foul because their blood supply is reduced. The brain commands and the heart responds by pumping harder and faster thereby increasing the blood pressure. We now have a runaway train and domino effect gets triggered.

The increased fluid pressure slowly begins to damage almost all our internal organs. One of the first to suffer will be the kidneys themselves – their vascular system suffers a breakdown (hypertensive Nephrosclerosis). Damaged kidneys further exasperate the already alarming situation and the person will require medical attention.